Windows 10 runs extremely slowly in Parallels 10

I'm running Parallels 10 on a 2014 MacBook Pro with OS X El Capitan (10.11.6). I have five virtual machines set up for various versions of Windows (7, 8, and 10).

For some reason, my Windows 10 VM runs extremely slowly – it boots, but then everything grinds to a halt (the Mac overall, not just the VM). Often, the only way out is to force shutdown and reboot.

The VM itself is a completely clean copy straight from Microsoft (indeed, I can never get it to run fast enough to actually do anything with it). My four other VMs all run perfectly fine, obviously on the same hardware, and I have all five configured identically.

I know that Parallels 11 advertises that it's ready for Windows 10, implying that previous versions aren't – but my Parallels 10 installation does list Windows 10 as an option in the VM configuration. So it would seem it's supported.

Is there anything I can do to fix this, or is the solution just to upgrade to Parallels 11 (even though in theory my current setup should work)?

I've had a better experience with Parallels 11 than I did with 10 so you might be worth considering an upgrade to improve the experienced.